playback and recording at the same time

Question

Life is Wonderful 2023-7-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1994803-playback-and-recording-at-the-same-time

评论： Life is Wonderful 2023-7-14

Hi there,

I need assistance playingback and recording simultaneously without actually preserving the stream as a recording on the disk. I am looking for playback from a remote machine, which is a target device, and screen capture playback streaming data is analysed in the backend system, where I pick up the video stream, convert to a frame, and histogram the defect sequence if I discover a defect.

Could you please provide me with a sample code and an idea? How can I complete such a task?

Thank you very much.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Vishnu 2023-7-12

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1994803-playback-and-recording-at-the-same-time#answer_1271738

在 MATLAB Online 中打开

Hi @Life is Wonderful,

You can utilize the VideoReader, implay and VideoWriter functions of MATLAB.

Here is some sample code on how to use these functions:

videoReader = VideoReader('path/to/video/file.mp4');
videoPlayer = implay('path/to/video/file.mp4');
videoWriter = VideoWriter('path/to/save/output.mp4', 'MPEG-4');

Setting equal framerates for VideoWriter instance and implay instance.

videoWriter.FrameRate = videoReader.FrameRate;
open(videoWriter);

Then run a while loop over the video which is to be read using the implay instance and use the writeVideo function to write the file data into the VideoWriter instance.

while hasFrame(videoReader)
    % Read the frame
    frame = readFrame(videoReader);
    
    % Perform some operations on the read frame
    
    % Write the frame to the video writer
    writeVideo(videoWriter, frame);
end

Close the instances you opened using the functions in the first step.

close(videoReader);
close(videoPlayer);
close(videoWriter);

You can check out the MATLAB documentation for these functions to have a better idea about the operations which you could perform on the video you read and the file you write in.

3 个评论
显示 1更早的评论隐藏 1更早的评论

Vishnu 2023-7-13

编辑：Vishnu 2023-7-13

在 MATLAB Online 中打开

Hi @Life is Wonderful,

I believe your approach is correct, I have a code snipped which can help.

function startRec
    disp('recording')
    Recorder = VideoWriter('result.mp4','MPEG-4');
    open(Recorder);
    videoObj = VideoReader('xylophone.mp4');
    frame = read(videoObj,1);
    RecTimer = timer("ExecutionMode", "fixedDelay", 'Period', 1/10, 'TimerFcn', @(~,~)writeVideo(Recorder,frame));
    start(RecTimer);
    pause(10);
    disp('stopped')
    stop(RecTimer);
    pause(0.5);
    delete(RecTimer);
    close(Recorder);
    delete(Recorder);
end

In this function i am reading an example video and then writing one of its frame. you can modify the timer callback function to read the latest frame of you live video and then write it to a file. here the timer function works like a while loop calling the callback after a certain time.

Hope this helps,Thank You.

Life is Wonderful 2023-7-14